As semiconductor devices have been miniaturized in recent years, not only a manufacturing apparatus but also an inspection device or an evaluation device are required to be highly accurate so as to respond to the above. A scanning electron microscope (hereinafter referred to as a CD-SEM) having a length measurement function is generally used for evaluating whether the geometry of a pattern formed on a semiconductor wafer is correct or not. In the CD-SEM, an electron beam is applied onto the wafer, an obtained secondary electron signal is image-processed and an edge of the pattern is discriminated from variation of light and shade to derive dimensions.
The semiconductor wafer is mounted on an XY stage, and the stage device is moved to thereby change positions to which the electron beam is applied and to perform inspections of various positions on the wafer. The positions to be inspected on the wafer can be discriminated by measuring positions of the stage. As a means for increasing the measurement accuracy, there exist a means using a mirror bar and a laser interferometer as shown in Patent Literature 1 and so on.
In Patent Literature 1, there is disclosed a means for adjusting positions by correction as countermeasures for deterioration of position accuracy due to occurrence of thermal deformation by temperature change of the stage and change between the stage and the mirror for the laser interferometer in the stage device using a linear motor.